Critical currents in high-quality YBaCuO ceramics investigated by magnetization, a.c. susceptibility and electrical transport

Abstract

Magnetization measurements are used to separate the intra- and intergrain critical currents of two dense, low-resistivity YBa 2Cu 3O 7 samples above 70 K. Transport (intergrain) critical currents, measured at 77 K, agree well with those deduced from magnetization. Estimates of critical currents from the magnetic field dependence of the imaginary susceptibility generally agree with those determined from the magnetization and electrical transport. At higher temperatures not all of the sample's volume is superconducting, which is reflected in the strong variation of intergrain critical current with temperature. The variation of intergrain (transport) critical current with magnetic field indicates weak-link intergrain coupling. Lower critical fields for bulk and grain respectively were determined.